Solid-state devices quasi-optically coupled in free space provide efficient schemes for combining power at microwave and millimeter-wave frequencies by eliminating losses associated with waveguide walls and feed networks. A typical quasi-optical oscillator or amplifier comprises a two-dimensional array of active devices forming a planar sheet with a reflection or transmission coefficient greater than unity. A resonator can be used to provide feedback to couple the devices together to form a high-power oscillator, or the active sheet can be placed between polarizers to form a grid amplifier. By integrating large numbers of devices into a grid, very large power can be achieved.
Grid amplifiers require the interaction of free space RF signal beams with an array of input antennas. After amplification, the signal is transmitted by a set of output antennas. Devices of this kind have been fabricated as hybrid structures for operation at low frequencies on the order of 10 GHz. However, the use of discrete components to build grid amplifier unit cells requires many connections that result in an amplifier that is very complex. Because of the limitations of prior art grid amplifiers, there is a need for a monolithic implementation of quasi-optical components that provides a grid amplifier that can be easily scaled to microwave and millimeter-wave frequencies, and is smaller, lighter, and substantially less costly than conventional phased-array systems.